// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
//
// A Status encapsulates the result of an operation.  It may indicate success,
// or it may indicate an error with an associated error message.
//
// Multiple threads can invoke const methods on a Status without
// external synchronization, but if any of the threads may call a
// non-const method, all threads accessing the same Status must use
// external synchronization.

#ifndef STORAGE_LEVELDB_INCLUDE_STATUS_H_
#define STORAGE_LEVELDB_INCLUDE_STATUS_H_

#include <algorithm>
#include <string>

#include "leveldb/export.h"
#include "leveldb/slice.h"

namespace leveldb {

class LEVELDB_EXPORT Status {
  public:
    // Create a success status.
    Status() noexcept : state_(nullptr) {}
    ~Status() { delete[] state_; }

    Status(const Status &rhs);
    Status &operator=(const Status &rhs);

    Status(Status &&rhs) noexcept : state_(rhs.state_) { rhs.state_ = nullptr; }
    Status &operator=(Status &&rhs) noexcept;

    // Return a success status.
    static Status OK() { return Status(); }

    // Return error status of an appropriate type.
    static Status NotFound(const Slice &msg, const Slice &msg2 = Slice()) {
        return Status(kNotFound, msg, msg2);
    }
    static Status Corruption(const Slice &msg, const Slice &msg2 = Slice()) {
        return Status(kCorruption, msg, msg2);
    }
    static Status NotSupported(const Slice &msg, const Slice &msg2 = Slice()) {
        return Status(kNotSupported, msg, msg2);
    }
    static Status InvalidArgument(const Slice &msg, const Slice &msg2 = Slice()) {
        return Status(kInvalidArgument, msg, msg2);
    }
    static Status IOError(const Slice &msg, const Slice &msg2 = Slice()) {
        return Status(kIOError, msg, msg2);
    }

    // Returns true iff the status indicates success.
    bool ok() const { return (state_ == nullptr); }

    // Returns true iff the status indicates a NotFound error.
    bool IsNotFound() const { return code() == kNotFound; }

    // Returns true iff the status indicates a Corruption error.
    bool IsCorruption() const { return code() == kCorruption; }

    // Returns true iff the status indicates an IOError.
    bool IsIOError() const { return code() == kIOError; }

    // Returns true iff the status indicates a NotSupportedError.
    bool IsNotSupportedError() const { return code() == kNotSupported; }

    // Returns true iff the status indicates an InvalidArgument.
    bool IsInvalidArgument() const { return code() == kInvalidArgument; }

    // Return a string representation of this status suitable for printing.
    // Returns the string "OK" for success.
    std::string ToString() const;

  private:
    enum Code {
        kOk              = 0,
        kNotFound        = 1,
        kCorruption      = 2,
        kNotSupported    = 3,
        kInvalidArgument = 4,
        kIOError         = 5
    };

    Code code() const { return (state_ == nullptr) ? kOk : static_cast<Code>(state_[4]); }

    Status(Code code, const Slice &msg, const Slice &msg2);
    static const char *CopyState(const char *s);

    // OK status has a null state_.  Otherwise, state_ is a new[] array
    // of the following form:
    //    state_[0..3] == length of message
    //    state_[4]    == code
    //    state_[5..]  == message
    const char *state_;
};

inline Status::Status(const Status &rhs) {
    state_ = (rhs.state_ == nullptr) ? nullptr : CopyState(rhs.state_);
}
inline Status &Status::operator=(const Status &rhs) {
    // The following condition catches both aliasing (when this == &rhs),
    // and the common case where both rhs and *this are ok.
    if (state_ != rhs.state_) {
        delete[] state_;
        state_ = (rhs.state_ == nullptr) ? nullptr : CopyState(rhs.state_);
    }
    return *this;
}
inline Status &Status::operator=(Status &&rhs) noexcept {
    std::swap(state_, rhs.state_);
    return *this;
}

}  // namespace leveldb

#endif  // STORAGE_LEVELDB_INCLUDE_STATUS_H_
